banger/README.md

# banger

Persistent Firecracker development VMs managed through a Go daemon, CLI, and TUI.

## Requirements
- Linux host with KVM (`/dev/kvm` access)
- Vsock support for post-SSH liveness reminders (`/dev/vhost-vsock`)
- Core VM lifecycle: `sudo`, `ip`, `dmsetup`, `losetup`, `blockdev`, `truncate`, `pgrep`, `chown`, `chmod`, `kill`
- Guest rootfs patching: `e2cp`, `e2rm`, `debugfs`
- Guest work disk creation/resizing: `mkfs.ext4`, `e2fsck`, `resize2fs`, `mount`, `umount`, `cp`
- SSH and logs: `ssh`
- Optional NAT: `iptables`, `sysctl`
- Image build: the bundled SSH key plus the tools above; `banger image build` no longer shells out through `customize.sh`

`banger` validates these per command and returns actionable errors instead of
assuming one workstation layout.

## Runtime Bundle
Runtime artifacts are no longer tracked directly in Git. Source checkouts use a
generated `./runtime/` bundle, while installed binaries use
`$(prefix)/lib/banger`.

The bundle contains:
- `firecracker`
- `banger-vsock-agent` for the guest-side vsock HTTP health agent and SSH reminder checks
- `bundle.json` with the bundle's default kernel/initrd/modules/rootfs paths
- a kernel, initrd, and modules tree referenced by `bundle.json`
- `rootfs-docker.ext4`
- `rootfs-docker.work-seed.ext4` when present, used to seed `/root` quickly on
  new VM creates
- `rootfs.ext4` when present
- `packages.apt`
- `id_ed25519`
- the helper scripts used by manual customization and installs

Bootstrap a source checkout from a local or published runtime archive. The
checked-in [`runtime-bundle.toml`](/home/thales/projects/personal/banger/runtime-bundle.toml)
is a template and intentionally ships with empty `url` and `sha256`.

If you need to create a local archive first, do that from a checkout or machine
that already has a populated `./runtime/` tree:
```bash
make runtime-package
cp dist/banger-runtime.tar.gz /path/to/fresh-checkout/dist/
```

In the fresh checkout:
```bash
cp runtime-bundle.toml runtime-bundle.local.toml
```

Edit `runtime-bundle.local.toml` to point at the staged archive and checksum:
```toml
url = "./dist/banger-runtime.tar.gz"
sha256 = "<sha256 printed by make runtime-package>"
```

Then bootstrap `./runtime/` with the local manifest copy:
```bash
make runtime-bundle RUNTIME_MANIFEST=runtime-bundle.local.toml
```

`url` may be a relative path, absolute path, `file:///...` URL, or HTTP(S)
URL. `make install` will not fetch artifacts for you.

## Build
```bash
make build
```

Run `make build` after `./runtime/` has been bootstrapped. It also rebuilds the
bundled `banger-vsock-agent` guest helper in `./runtime/`.

Install into `~/.local/bin` by default, with the runtime bundle under
`~/.local/lib/banger`:
```bash
make install
```

After `make install`, the installed `banger` and `bangerd` do not need the repo
checkout to keep working.

## Basic VM Workflow
Create and boot a VM:
```bash
banger vm create --name calm-otter --disk-size 16G
```

Check host/runtime readiness before creating VMs:
```bash
banger doctor
```

List VMs:
```bash
banger vm list
```

Inspect a VM:
```bash
banger vm show calm-otter
banger vm stats calm-otter
```

SSH into a running VM:
```bash
banger vm ssh calm-otter
```

When the SSH session exits normally, `banger` checks the guest over vsock and
reminds you if the VM is still running.

Inspect host-reachable listening ports for one or more running VMs:
```bash
banger vm ports calm-otter buildbox
```

Stop, restart, kill, or delete it:
```bash
banger vm stop calm-otter
banger vm start calm-otter
banger vm restart calm-otter
banger vm kill --signal TERM calm-otter
banger vm delete calm-otter
```

Update stopped VM settings:
```bash
banger vm set calm-otter --memory 2048 --vcpu 4 --disk-size 32G
```

Lifecycle and `set` actions also accept multiple VM refs and run them
concurrently:
```bash
banger vm stop calm-otter buildbox api-1
banger vm kill --signal KILL aa12bb34 cc56dd78
banger vm set --nat web-1 web-2 web-3
```

Launch the TUI:
```bash
banger tui
```

## Daemon
The CLI auto-starts `bangerd` when needed.

Useful daemon commands:
```bash
banger daemon status
banger daemon socket
banger daemon stop
```

`banger daemon status` prints the daemon PID, socket path, daemon log path, and
the built-in DNS listener address.

State lives under XDG directories:
- config: `~/.config/banger`
- state: `~/.local/state/banger`
- cache: `~/.cache/banger`
- runtime socket: `$XDG_RUNTIME_DIR/banger/bangerd.sock`

Installed binaries resolve their runtime bundle from `../lib/banger` relative to
the executable. Source-checkout binaries resolve it from `./runtime` next to the
repo-built `./banger`. You can override either with `runtime_dir` in
`~/.config/banger/config.toml` or `BANGER_RUNTIME_DIR`.

Useful config keys:
- `log_level`
- `runtime_dir`
- `tap_pool_size`
- `firecracker_bin`
- `namegen_path`
- `customize_script` (manual helper compatibility; `banger image build` is Go-native)
- `vsock_agent_path`
- `default_rootfs`
- `default_work_seed`
- `default_base_rootfs`
- `default_kernel`
- `default_initrd`
- `default_modules_dir`
- `default_packages_file`

Guest SSH access always uses the private key shipped in the resolved runtime
bundle. `ssh_key_path` is no longer a supported override for `banger vm ssh`,
VM start key injection, or daemon guest provisioning.

## Doctor
`banger doctor` runs the same readiness checks the Go control plane uses for VM
start, host-integrated features, and image builds. It reports runtime bundle
state, core VM host tools, current feature readiness, and image-build
prerequisites in a concise pass/warn/fail list.

Use it when bringing up a new machine, after changing the runtime bundle, or
before adding new host-integrated VM features.

## Logs
- daemon lifecycle logs: `~/.local/state/banger/bangerd.log`
- raw Firecracker output per VM: `~/.local/state/banger/vms/<vm-id>/firecracker.log`
- raw image-build helper output: `~/.local/state/banger/image-build/*.log`

`bangerd.log` is structured JSON. Set `log_level` in
`~/.config/banger/config.toml` or `BANGER_LOG_LEVEL` to one of `debug`,
`info`, `warn`, or `error`.

## Images
List images:
```bash
banger image list
```

Build a managed image:
```bash
banger image build --name docker-dev --docker
```

Rebuilt images install a pinned `mise` at `/usr/local/bin/mise`, activate it
for bash login and interactive shells, install `opencode` through `mise`,
configure `tmux-resurrect` plus `tmux-continuum` for `root` with periodic
autosaves and manual-only restore by default, and bake in the
`banger-vsock-agent` systemd service used by the post-SSH reminder path and
guest health checks. They
also emit a `work-seed.ext4` sidecar that lets new VMs clone a prepared `/root`
work disk instead of rebuilding it from scratch on every create.

Show or delete images:
```bash
banger image show docker-dev
banger image delete docker-dev
```

`banger` auto-registers the bundled `default_rootfs` image when it exists. If
the bundle does not include a separate base `rootfs.ext4`, `image build` falls
back to using `rootfs-docker.ext4` as its default base image.

## Networking And DNS
Enable NAT when creating or updating a VM:
```bash
banger vm create --name web --nat
banger vm set web --nat
banger vm set web --no-nat
```

NAT is applied by the Go control plane using host `iptables` rules derived from
the VM's current guest IP and TAP device. The remaining shell helpers also
route NAT changes through `banger` instead of a standalone shell NAT script.

`bangerd` also serves a tiny authoritative DNS service on `127.0.0.1:42069`
for daemon-managed VMs. Known `A` records resolve `<vm-name>.vm` to the VM's
guest IPv4 address. Integrate your local resolver separately if you want
transparent `.vm` lookups on the host.

`banger vm ports` asks the guest-side `banger-vsock-agent` to run `ss`, then
prints host-usable `<hostname>.vm:port` endpoints plus the owning
process/command. TCP listeners get a short best-effort HTTP probe; when the
probe sees a real HTTP response, the command includes a clickable
`http://<hostname>.vm:port/` URL. Older images without `ss` may need rebuilding
before `vm ports` works.

## Storage Model
- VMs share a read-only base rootfs image.
- Each VM gets its own sparse writable system overlay for `/`.
- Each VM gets its own persistent ext4 work disk mounted at `/root`.
- When an image has a `work-seed.ext4` sidecar, new VM creates clone that seed
  and only resize it when needed. Older images still work, but create more
  slowly because `/root` must be built from scratch.
- The daemon can keep a small idle TAP pool warm in the background so VM create
  does not need to synchronously create a fresh TAP every time. `tap_pool_size`
  controls the pool depth.

## Architecture Notes
The Go daemon is the primary control plane. VM host integrations such as the
built-in `.vm` DNS service, NAT, and `/root` work-disk wiring now sit behind a
capability pipeline in the daemon instead of being open-coded through the VM
lifecycle. Guest boot-time files and mounts are rendered through a structured
guest-config builder rather than ad hoc `fstab` string mutation.

That split is intentional: future host-integrated features should plug into the
daemon capability path and `banger doctor` checks first, with the remaining
shell helpers treated as manual workflows rather than architecture drivers.
- Stopping a VM preserves its overlay and work disk.

## Rebuilding The Repo Default Rootfs
`packages.apt` controls the base apt packages baked into rebuilt images,
including guest tools such as `ss` used by `banger vm ports`.

To rebuild the source-checkout default image in `./runtime/rootfs-docker.ext4`:
```bash
make rootfs
```

That rebuild also regenerates `./runtime/rootfs-docker.work-seed.ext4`, which
the daemon uses to speed up future `vm create` calls.

If your runtime bundle does not include `./runtime/rootfs.ext4`, pass an
explicit base image instead:
```bash
./make-rootfs.sh --base-rootfs /path/to/base-rootfs.ext4
```

If the package manifest changed and you want a fresh source-checkout image:
```bash
rm -f ./runtime/rootfs-docker.ext4 ./runtime/rootfs-docker.ext4.packages.sha256
make rootfs
```

`make rootfs` expects a bootstrapped runtime bundle. If `./runtime/rootfs.ext4`
is not available, pass an explicit `--base-rootfs` to `./make-rootfs.sh`.
Existing VMs keep using their current image and disks; rebuilds only affect VMs
created from the rebuilt image afterward.

## Experimental Void Rootfs
There is also a separate, opt-in builder for an experimental Void Linux guest
path:
```bash
make rootfs-void
```

That writes:
- `./runtime/rootfs-void.ext4`
- `./runtime/rootfs-void.work-seed.ext4`

This path is intentionally local-only and does not change the default Debian
image flow. It reuses the current runtime bundle kernel, initrd, and modules,
but builds a lean `x86_64-glibc` Void userspace with:
- `bash` installed for interactive/admin use
- `openssh` enabled under runit
- the bundled `banger-vsock-agent` health agent enabled under runit
- `root` normalized to `/bin/bash` while keeping `/bin/sh` as the distro's system shell
- a generated `/root` work-seed for fast creates

It does not install the Debian-oriented extras from rebuilt default images:
- no Docker
- no `mise`
- no `opencode`
- no tmux plugin defaults

The builder fetches official static XBPS tools and packages from the Void
mirror during the build. It currently supports only `x86_64-glibc`.

The package set comes from [`packages.void`](/home/thales/projects/personal/banger/packages.void).
You can override the mirror, size, or output path directly:
```bash
./make-rootfs-void.sh --mirror https://repo-default.voidlinux.org --size 2G
```

The fastest local iteration loop does not require changing your default image
config at all:
```bash
make rootfs-void
make void-register
./banger vm create --image void-exp --name void-dev
./banger vm ssh void-dev
```

There is also a smoke path for the experimental image:
```bash
make verify-void
```

`make void-register` uses the unmanaged image registration path to create or
update a `void-exp` image record in place, so repeated rebuilds do not require
editing `~/.config/banger/config.toml`.

There is also a one-step helper target:
```bash
make void-vm VOID_VM_NAME=void-a
```

If you really want the Void image to become your default for `vm create`
without `--image`, use the checked-in override template at
[`examples/void-exp.config.toml`](/home/thales/projects/personal/banger/examples/void-exp.config.toml)
and merge its four settings into `~/.config/banger/config.toml`.

`banger image build` remains Debian-only in this pass. Do not point
`default_base_rootfs` at the Void artifact yet.

## Registering Unmanaged Images
You can also register any local rootfs as an unmanaged image record without
changing global defaults:
```bash
banger image register --name local-test --rootfs /abs/path/rootfs.ext4
```

Optional paths let you point at an existing work seed, kernel, initrd, modules,
and package manifest:
```bash
banger image register \
  --name void-exp \
  --rootfs ./runtime/rootfs-void.ext4 \
  --work-seed ./runtime/rootfs-void.work-seed.ext4 \
  --packages ./packages.void
```

If an unmanaged image with the same name already exists, `image register`
updates it in place so future `vm create --image <name>` calls pick up the new
artifacts immediately.

## Maintaining The Runtime Bundle
The checked-in [`runtime-bundle.toml`](/home/thales/projects/personal/banger/runtime-bundle.toml)
is a template. Keep `bundle_metadata` accurate there, but use a separate local
manifest copy when you need concrete `url` and `sha256` values for bootstrap
testing or publication.

Package a local `./runtime/` tree into an archive:
```bash
make runtime-package
```

That writes `dist/banger-runtime.tar.gz` and prints its SHA256 so you can update
a local manifest copy before testing bootstrap changes or publishing the
archive elsewhere.

## Benchmarking Create Time
Benchmark the current host's `vm create` wall time plus first-SSH readiness:
```bash
make bench-create
```

Pass options through `ARGS`, for example:
```bash
make bench-create ARGS="--runs 3 --image docker-dev"
```

The benchmark prints JSON with:
- `create_ms`: wall time for `banger vm create`
- `ssh_ready_ms`: wall time from create start until `banger vm ssh <vm> -- true`
  succeeds

## Remaining Shell Helpers
The runtime VM lifecycle is managed through `banger`. The remaining shell scripts are not the primary user interface:
- `customize.sh`: manual reference flow for rootfs customization; `banger image build` is now Go-native, but the script still reads
  assets from `BANGER_RUNTIME_DIR` and stores transient state under
  `BANGER_STATE_DIR`/XDG state
- `make-rootfs.sh`: convenience wrapper for rebuilding `./runtime/rootfs-docker.ext4`
- `interactive.sh`: manual one-off rootfs customization over SSH
- `packages.sh`: shell helper library
- `verify.sh`: smoke test for the Go workflow (`./verify.sh --nat` adds NAT coverage)